About this replacement
Asus ZenFone 7 / ZenFone 7 Pro — 3.85V Li-Polymer Replacement Battery (C11P1904)
This is a 3.85V, 4800mAh Li-Polymer replacement battery for the Asus ZenFone 7 and ZenFone 7 Pro smartphones (model numbers ZS670KS and ZS671KS). It replaces OEM part numbers C11P1904 and 0B200-03740200. The cell matches the original dimensions at 74.40 × 64.54 × 6.00mm, so it seats correctly in the battery bay without modification.
- ZS670KS and ZS671KS compatibility: Both the ZenFone 7 and ZenFone 7 Pro use the same C11P1904 cell with matching voltage rail, connector footprint, and BMS handshake — a single part number covers both models.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on ZS671KS hardware. The BMS accepted the charge IC handshake without fault codes, and voltage held stable across modem and display load.
- Fuel gauge recalibration on first use: Disable fast charging for the first complete discharge-charge cycle after installation. The fuel gauge IC calibrates its discharge curve against the new cell during this cycle — skipping it on a high-current charge pushes current into an uncalibrated cell and can cause early percentage errors.
Sudden shutdown at 20–30% on the ZenFone 7 after a cell swap
This happens because the fuel gauge IC still holds the discharge curve from the degraded original cell. When the new cell's actual voltage drops under modem or display load, the OS receives a voltage reading it maps to near-empty on the old curve — and the phone shuts down before the percentage counter reaches zero. The fix is one full uninterrupted discharge-charge cycle with fast charging off. After that cycle, the coulomb counter resets against the new cell's actual curve and the shutdowns stop.
USB-PD fast charging not accepted on the first cycle after replacement
On the first charge after installation, the ZenFone 7's charge IC sometimes fails to negotiate the USB-PD fast charge contract with the new cell's BMS — the phone charges slowly or falls back to 5W standard charging. This is a one-cycle behaviour caused by the BMS completing its initial handshake with the charge IC. Plug into the same charger after that first full cycle and fast charging resumes at the correct wattage. If it persists beyond the second cycle, check that the cable supports USB-PD at 18V.